1. Field of the Invention
This invention relates to an optical apparatus having a motor control device for controlling the driving of a stepping motor.
2. Related Background Art
In lens driving using a stepping motor, it is popular to calculate a reference position, i.e., an initial position, by some method or other, and control the motor by using the number of driving steps in conjunction with the reference position.
The accuracy required of lens driving is of the amount of several microns, and in order to detect it, the movement of a lens has been enlarged by the use of a construction which enlarges the movement of the lens, for example, a lever or the like, and the detection of the initial position has been effected by a conventional leaf switch or the like.
In the above-described example of the prior art, the movement of the lens is enlarged by a lever or the like and therefore, good accuracy has not been obtained due to the influence of the back-lash between parts. Since switching timing of the leaf switch, i.e., the relation between the contact pressure and the contact resistance between contacts, is liable to become irregular, it has been difficult to detect the position of the lens with good accuracy. Further, when the position control of the lens is to be accomplished using the position detected by the switch as the initial position, there also arises the problem that a loss of synchronism is liable to be caused. This is because near the aforementioned initial position, a load for driving the switch member is applied to the stepping motor. Accordingly, in the prior-art a lens driving device that is capable of, highly accurate positioning and which determines the driving starting position stably and accurately, has been impossible.